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I04O                          Appendix VI.

engaging with the lever L and putting one or other of the pair of

bevels hi gear.    The head B can be advanced by hand wheels w

\i                         and T, slewed to suit taper holes, or the work may be lifted for

examination by means of the lever N.

;                              A grinding rig is also shewn in Fig. 938 for a small three-

1                         throw crank shaft.    Special heads m and r are bolted to the table

;                         (see Fig. 935), and these carry driving bosses p q> the weight s

'J                         acting as a balance.    The emery wheel must be of large diameter

j                         so as to reach the work.

i
I

i]                               P. 202.    Automatic   Turret  Lathe.—Alfred Herbert's

/:                          Full-automatic Screw Machine is illustrated in Figs. 939, 940,

jj                          941, and 942.    The first figure indicates by side and end eleva-

11                          tion the arrangement of the machine, which obtains its title from

,*                          the fact that it is largely occupied in the production of bolts,

t,                          studs, and screws, though various forms of handles and spindles

'!                          may also be cut from the solid bar or stock, and all this with

practically no attention whatsoever.    It will be seen from Fig. 939

>k                          that there are two sets of driving gear from the overhead counter-

I                          shaft; at A with crossed and open belts so as to rotate by spur

' |                          gear the hollow mandrel, and at B through worm gear to the cam

1                          shaft D.    The drum E is supplied with cam plates, which strike

|                          the studs  at K for the purpose of causing the  stock or bar

f1                          within the hollow mandrel to advance to the correct length, when

^                          it is gripped by the collet or chuck; while the cam disc M acts

'(,                          upon a lever, which gives a backward or forward rotation of shaft

tj                          N, thus moving the forks at p, and producing the forward or

/j                          reverse rotation of the mandrel, according to which belt is on the

' y                          fast pulley.    Another cam plate G acts upon the levers H and j,

'!                         that put the slides at Q in position for parting the finished work,

the tools being shewn at R, and the turret slide is advanced and

withdrawn for the operations of turning, screwing, rounding, &c,

, I                         by means of cam plates upon the drum F.

''J                               Referring now to Fig. 940, which is a section and plan of the

f ;f *                          headstock: A is the driving pulley, and B c loose pullies, one for

|                          the crossed and the other for the open belt, and the fast pulley A

, i                          is slightly larger than the others, so as to cause a better grip when

'2                          driving.    The lever D, previously mentioned, rocks to right or